The present invention relates generally to a foil keyboard and in particular to a foil keyboard which secures the keys and their electrical contacts against unauthorized access.
At the present time a range of equipment is employed in Automatic Teller Machines (ATM) and for electronic funds transfer (EFT or electronic cash) for data entry or output. Certain security provisions are associated with this equipment in order to be able to avoid any possible undesired manipulation. The security of confidential information and the protection of data input and output from possible influences or manipulation is generally effected by means of electronic or mechanical security measures, such as, for example, the physical incorporation of various security-relevant components into one security module. Particularly security-sensitive components or modules are, in particular, data input keyboards, key memory for storing confidential keys, e.g. for coding data transfer and security circuits for electronic protection of security-relevant components. Thus, keyboards in particular, have to be protected against simultaneous disclosure of input data, such as a personal identification number (PIN).
A security module for an electronic funds transfer system is known from European Patent Application EP A-0186981. The security module is located in an impact-resistant housing. The module has a PIN entry block and can key confidential data, such as, for example, the PIN, and thus offers access to these data to other equipment.
An extensive study of the physical security of systems for an electronic funds transfer is known from the IBM document xe2x80x9cPhysical Security for the IBM Transaction Security Systemxe2x80x9d, IBM Charlotte, N.C., 28257, May 6, 1991 by G. P. Double. This document proposes various test methods and possible protective measures. In particular, this document teaches the use of a so-called Intrusion Detection Screen for the electronic detection of mechanical penetration of the film. The intrusion detection screen comprises a flexible circuit board with thin meandering conductor paths or a combination of flexible circuit board with thin meandering conductor paths and a printed circuit board with integrated thin meandering conductor paths. If the conductor paths are short-circuited or destroyed by mechanical action, such as, for example, penetration or tearing, this will be recognized by one of the inbuilt security switches. A monitoring logic connected to the intrusion detection screen recognizes changes in the resistance network of the protective film and sets off a suitable alarm which can lead, for example, to the deletion of security-relevant data.
To make manipulations at keyboards, which are intended, for example, for use in ATMs or electronic funds transfer, more difficult, a range of measures is known which will enhance data security. A known method for this is to encapsulate the electronics to be protected including the keyboard.
Apart from the encapsulation method, it is also usual to embed the security logic with data memory and the keyboard required for data input, in a housing and to wrap the housing in a security film. The security film is here designed in such a way that removal of or damage to the security film will lead to a corresponding alarm.
Apart from the data memory, which contains any security-relevant data, the keyboard must be protected so as to prevent or make more difficult the unauthorized xe2x80x98theftxe2x80x99 of the information input, such as, for example, a personal identification number (PIN). Total encapsulation of the keyboard, however, is not possible, since the keyboard must be at least partially accessible for input.
A security keyboard is known from the IBM Technical Disclosure Bulletin, Vol.33, No.9, February 1991, pp. 448-449, in which the contact portions of the keyboard are disposed within a region protected by a security film while the keys themselves remain outside the protected region and are thus accessible to the user. The arrangement of the keys at the security film is such that an unauthorized mechanical access to the key contacts at the security film cannot be detected.
Another prior art security keyboard with a security system is shown in FIG. 1. That security keyboard consists of a printed circuit board (PCB) 1 having a security module 2 containing all security relevant functions encapsulated with a security film that is connected to one inbuilt security switch (not shown). When the key 4 is pressed the metal dome 5 snaps in and shortens the electrical contacts 3 for the key, which will be recognized by the inbuilt security switch as a valid key stroke. Furthermore, the PCB 1 has one or more security electrical contacts 6 with an assigned metal dome 7. The security electrical contact 6 is connected to an in-built security switch. When keyboard is assembled and mounted using screws and nuts 12, the cover 11, spacer 10, and gasket 9 force metal dome 7 to snap in and to shorten security contacts 6. This indicates the in-built security switch that the keyboard is assembled correctly. Otherwise the security switch will erase all security-relevant data. Attempts to manipulate the keyboard, for example recording of input data, e.g. PINs, requires mechanical access to the keys 4 and their contacts 3. This requires disassembling of the keyboard which leads the electrical contact 6 from the closed to the open state. This activates the in-built security switch, the electrical contact 6 is connected to and erases all security-relevant data. A disadvantage of that security keyboard is that a weakening of the spring force of the metal dome can unintentionally activate the security switch resulting in cancellation of all security relevant data. Furthermore, the security keyboard is complex in structure and assembly.
It is therefore a purpose of the present invention to provide a foil keyboard with a simple and low cost security system for detecting unauthorized mechanical access to the key contacts however avoiding the disadvantages of prior art security systems.
This purpose is solved by the features of the independent claims. Preferred embodiments of the present invention are laid in the dependent claims.
The present invention discloses a foil keyboard with a security system for detecting and preventing unauthorized mechanical access to the key contacts. The foil keyboard comprising a foil having for each key an elastic key spring area in which an electrical contact is arranged, a printed circuit board (PCB) having electrical contacts that are contacted by the electrical contacts of the keys during the key travel, and a security system which is integrated into the foil and the PCB. The security system itself comprises a first arrangement of conductors disposed at the inner surface of the foil and placed around the key entry block area, a second arrangement of conductors disposed at the PCB, electrical contacts arranged at the conductors of the foil and the PCB for electrically connecting the first and second arrangement of conductors, and a security switch for providing power means and detections means. Each conductor of the first and second arrangement of conductors is followed by short non-conductive area. The first and second arrangements are arranged to each other such that each non-conductive area of the first arrangement is electrically bridged via an electrical contact with an opposite conductor of the second arrangement of conductors and each non-conductive area of the second arrangement of conductor is electrically bridged by via the electrical contact with an opposite conductor of the first arrangement of conductors in order to built a closed circuitry between first and second arrangement of conductors when power is applied. The closed circuit between keyboard foil and PCB forms a security grid that secures that unauthorized mechanical accesses against key contacts are recognized by the detecting means of the security switch. This inventive foil keyboard provides a simple and low cost keyboard combining the security standard for protecting security-relevant data inside the keyboard as well as providing additional security requirements with respect to unauthorized mechanical access to the key contacts without requiring additional components.